<template>
  <div>
    <h1>当前求和为：{{sum}}</h1>
    <select v-model.number="n">
      <option value="1">1</option>
      <option value="2">2</option>
      <option value="3">3</option>
    </select>
    <button @click="increment">+</button>
    <button @click="decrement">-</button>
    <button @click="incrementOdd">和为奇数时加</button>
    <button @click="incrementWait">过一段时间再加</button>
  </div>
</template>

<script>
export default {
  name:"Count",
  data(){
    return {
      n:1,
      sum:0
    }
  },
  methods:{
    increment(){
      this.sum += this.n;
    },
    decrement(){
      this.sum -= this.n;
    },
    incrementOdd(){
      if(this.sum % 2 !== 0){
        this.sum += this.n;
      }
    },
    incrementWait(){
      setTimeout(() => {
        this.sum += this.n;
      }, 500);
    }
  },
  mounted(){
    console.log(this);
  }
}
</script>

<style>
  button{
    margin-left: 5px;
  }
</style>